Proponents of legalized marijuana have won phenomenal gains over the last decade. Despite the federal government's continuing criminalization of the drug, several states including California, Colorado and Massachusetts, have voted to legalize its recreational use.

Most people are aware of the social and political controversies the marijuana legalization movement stirs. But there's another side to this roiling issue: the health effects of marijuana, particularly for your teeth and gums. What may be lost beneath the more exciting headlines about ballot initiatives is the growing evidence that habitual marijuana use may increase the risk and severity of periodontal (gum) disease.

Gum disease is a bacterial infection caused by dental plaque, a thin film of bacteria and food particles that accumulates on teeth. The spreading infection triggers inflammation, a normal bodily response to disease that's ordinarily beneficial. But if the inflammation becomes chronic it weakens the gums' attachment to the teeth. This can create voids or periodontal pockets of infection around the teeth. The disease can eventually damage the underlying bone, which could accelerate tooth loss.

Poor oral hygiene is the biggest factor for an increased risk of gum disease; thinner gum tissue (an inherited condition or related to poor tooth position) is another factor, as well as lifestyle habits like tobacco use or excessive alcohol consumption. Add marijuana to the list: there's now some evidence that its use increases the risk for more severe periodontal pockets if the disease occurs.

In a recent study, researchers with the Columbia University College of Dental Medicine reviewed statistics on the care for nearly 2,000 adult patients; a quarter of those in the study were frequent marijuana users. The marijuana users proportionately had deeper periodontal pocket occurrences than the rest of the patients in the study that didn't use the drug.

The study doesn't say that marijuana causes periodontal (gum) disease. But it does suggest that marijuana use might increase its severity. As with other substances and practices in our society, marijuana use comes with a caveat: it may be legal where you live, but it may not necessarily be good for your health.